1. Field of the Invention
The present invention relates to a surgical device and method. More specifically, it is a device assembly and method adapted to form a circumferential conduction block along a circumferential region of tissue along a posterior left atrial wall and surrounding a pulmonary vein.
2. Description of the Related Art
Many abnormal medical conditions in humans and other mammals have been associated with disease and other aberrations along the walls that define several different body spaces. In order to treat such abnormal wall conditions of the body spaces, medical device technologies adapted for delivering specific forms of ablative energy to specific regions of targeted wall tissue from within the associated body space have been developed and disclosed.
Cardiac arrhythmias, and atrial fibrillation in particular, persist as common and dangerous medical ailments, especially in the aging population. In patients with normal sinus rhythm, the heart, which is comprised of atrial, ventricular, and excitatory conduction tissue, is electrically excited to beat in a synchronous, patterned fashion. In patients with cardiac arrhythmia, abnormal regions of cardiac tissue do not follow the synchronous beating cycle associated with normally conductive tissue in patients with sinus rhythm. Instead, the abnormal regions of cardiac tissue aberrantly conduct to adjacent tissue, thereby disrupting the cardiac cycle into an asynchronous cardiac rhythm. Such abnormal conduction has been previously known to occur at various regions of the heart, such as, for example, in the region of the sino-atrial (SA) node, along the conduction pathways of the atrioventricular (AV) node and the Bundle of His, or in the cardiac muscle tissue forming the walls of the ventricular and atrial cardiac chambers.
Cardiac arrhythmias, including atrial arrhythmia, may be of a multiwavelet reentrant type, characterized by multiple asynchronous loops of electrical impulses that are scattered about the atrial chamber and are often self propagating. In the alternative or in addition to the multiwavelet reentrant type, cardiac arrhythmias may also have a focal origin, such as when an isolated region of tissue in an atrium fires autonomously in a rapid, repetitive fashion. These foci may act as either a trigger of paroxysmal atrial fibrillation or may sustain the fibrillation. Recent studies have suggested that focal arrhythmia often originates from a tissue region along the pulmonary veins of the left atrium, and even more particularly in the superior pulmonary veins.
Percutaneous catheter ablation techniques have been disclosed which use end-electrode catheter designs with the intention of ablating and thereby treating focal arrhythmias in the pulmonary veins. These ablation procedures are typically characterized by the incremental application of electrical energy to the tissue to form focal lesions designed to ablate the focus and thereby interrupt the inappropriate conduction pathways.
One example of a focal ablation method intended to destroy and thereby treat focal arrhythmia originating from a pulmonary vein is disclosed by Haissaguerre, et al. in “Right And Left Atrial Radiofrequency Catheter Therapy Of Paroxysmal Atrial Fibrillation” in Journal of Cardiovascular Electrophysiology 7(12), pp. 1132-1144 (1996). Haissaguerre, et al. disclose radiofrequency catheter ablation of drug-refractory paroxysmal atrial fibrillation using linear atrial lesions complemented by focal ablation targeted at arrhythmogenic foci in a screened patient population. The site of the arrhythmogenic foci were generally located just inside the superior pulmonary vein, and were ablated using a standard 4 mm tip single ablation electrode.
In another focal ablation example, Jais et al. in “A Focal Source Of Atrial Fibrillation Treated By Discrete Radiofrequency Ablation” Circulation 95:572-576 (1997), applies an ablative technique to patients with paroxysmal arrhythmias originating from a focal source. At the site of arrhythmogenic tissue, in both right and left atria, several pulses of a discrete source of radiofrequency energy were applied in order to eliminate the fibrillatory process.
There is a need, however, for a circumferential ablation device assembly and method adapted to electrically isolate a substantial portion of a posterior left atrial wall from an arrhythmogenic focus along a pulmonary vein. In particular there is still a need for such an assembly and method which provides a circumferential ablation member secured to the distal end of an elongate catheter body and which includes an ablation element adapted to form a circumferential conduction block along a circumferential region of tissue which either includes the arrhythmogenic focus or is between the arrhythmogenic focus and a substantial portion of the posterior left atrium wall.